Effect of Surface Treatment on Interface Properties of Bonded Graphene/GaN Structures

Heterostructures with new material combinations are being investigated to improve device functionality, especially hybrid two-dimensional/three-dimensional (2D/3D) material structures. In this report, bonded graphene/GaN structures with various GaN surface pretreatment conditions are studied using temperature-dependent current–voltage and x-ray photoelectron spectroscopy (XPS) measurements. The HCl and H 2 + N 2 , H 2 , and O 2 plasma treatments explored here affect the GaN surface states and oxidation, which in turn affect the diode IV performance. The barrier heights for all samples were similar at ~0.8 eV, and this finding was supported by XPS measurements. The O 2 plasma treated sample formed a thicker oxide interlayer as evidenced by XPS measurements and had a higher series resistance. Some of the diodes exhibited parallel current leakage probably via GaN dislocations. Ideality factors for all samples were less than 2, with the H 2 + N 2 plasma treated sample having the lowest ideality factor of 1.25 at 115°C, suggesting this plasma treatment passivates the GaN surface states more effectively.